80. Remove Duplicates from Sorted Array II

Follow up for "Remove Duplicates":
What if duplicates are allowed at most twice?

For example,
Given sorted array nums = [1,1,1,2,2,3],

Your function should return length = 5, with the first five elements of nums being 1, 1, 2, 2 and 3. It doesn't matter what you leave beyond the new length.

解题思路：由于每个元素至多出现两次，所以只需要判断nums[i]是否等于nums[i-2]，如果是说明该数字出现的次数超过了2次，否则，该数字出现的次数少于2次，将它加到结果数组中。

class Solution {
public:
    int removeDuplicates(vector<int>& nums) {
        int i=0;
        for(int num: nums){
            if(i<2||num>nums[i-2])
            nums[i++]=num;
        }
        return i;
    }
};